As far as the second Silver Star goes it may be that he or someone else in the family sent for and received a 2nd Silver Star Medal. The govt. will reissue and send replacements when requested one time. Since you only have a copy of one citation it will be hard to know for sure.
He also would have been awarded the Purple Heart for wounds received against an enemy force not for a domestic scuffle aboard ship. While he was stabbed aboard ship by a fellow sailor does not merit an award. Most likely the story as it got passed down through the famly over the years got changed little by little. It happens more than you know so your not alone in that category.
Being that you are a direct decendant you can request his military records through NARA and should receive copies of everything they have on him, including what and how many awards/medals/citations he received, theaters of operation and more.
Is it possible someone else in the family has the rest of his documents?
I hope this helped you some.